The design of repellent surfaces has been subject of intense research that has led to the development of superhydrophobic surfaces, which show resistance to water, or superomniphobic surfaces, which show resistance to water and higher-surface tension organic liquids. Generally, the underlying principle of all these approaches is the reduction of contact points of a liquid droplet by the introduction of carefully designed roughness features to a solid surface. Hence, the general approach has been to make high aspect ratio structures, such as posts and pillars, that can control the amount of contact points with the material to be repelled. However, these structures suffer from poor mechanical stability and generally do not repel low-surface-tension liquids.
Recently, Applicants have developed lubricated liquid-infused porous materials that can repel even low-surface-tension aliphatic oils. These slippery liquid-infused porous surfaces (SLIPS) generally provide a porous substrate with high affinity to the lubricating liquid, so that the lubricating liquid layer is not displaced from the solid's surface. Such surfaces have shown to be highly repellent to a wide variety of materials providing extremely low sliding angles-even for liquids that form contact angles that are smaller than 90° on a flat substrate of the same material or the same surface functionalization and therefore generally wet and stick to most surfaces (e.g., low-surface-tension liquids). Compared to superhydrophobic materials that require high dynamic contact angles to allow a liquid to roll off the surface, such SLIPS structures eliminate this condition but capitalize on minimizing the contact angle hysteresis. However, such SLIPS structures can suffer from loss of the ultra-repellency as the lubricating liquid evaporates or shears away over time exposing the underlying porous substrate. Hence, previous efforts utilized adding a reservoir that can replenish the lubricating liquid.